%%
%% The LaTeX Companion, 3ed
%%
%% Example 8-2-14 on page I-594 in "overpic --- Graphic annotation made easy".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{135.0pt}

%StartShownPreambleCommands
\usepackage{overpic,pict2e,color}
%StopShownPreambleCommands

\begin{document}
\begin{Overpic}[grid,rel=50,tics=10]
               {$ \displaystyle \sum_{i=1}^n x_i = A + B $}
  \color{blue} \Vector(40,5)(32,9)
  \put(42,3){\footnotesize\itshape some explanation}
\end{Overpic}
\end{document}
